First-class Forged Rolling Mill Rolls

The technical capacity of steelmaking facilities enables NKMZ to produce up to 200t of liquid metal and cast ingots weighing from 1,6t to 170t.

Steelmaking facilities of NKMZ are composed of the following equipment: 

• 1 electric arc furnace EAF with the capacity of 50t; 
• 2 electric arc furnaces EAF with the capacity of 12t; 
• 1 electric arc furnace EAF with the capacity of 5t; 
• 2 after-furnace ladle steel treatment units “Ladle-furnace”; 
• 4 vacuum degasser (VD and VOD).

 Steel ingot casting may be performed either in vacuum by top pouring or in the air by bottom pouring.

Forging facilities of NKMZ are composed of the following equipment: 

• Automated forging complexes with Hydraulic Press 10000 TF capacity;
• Automated forging complexes with Hydraulic Press 5000 TF capacity;
• Automated forging complexes with Hydraulic Press 3000 TF capacity;
• High-efficient reheating furnaces.

The technical capacity of forging facilities enables NKMZ to produce forgings weighing from 0,2t up to 110t.

We ensure the following purity of steel: 

• oxygen O2 15…35 ppm 
• hydrogen H2 <1,5 ppm 
• nitrogen N2 40…80 ppm 

NKMZ uses the following groups of steel for manufacturing of rolling-mill rolls:    

Features of NKMZ heat treatment include automatic temperature measuring systems in all furnaces and sprayers, application of hight-progressive models to control speeds of heating and cooling and automatic control of heating and cooling. 

Backup rolls and work rolls for hot-rolling mills: 

• Isothermal annealing is performed in horizontal gas furnaces;
• Hardening of whole backup roll body is performed by quenching in water-air sprayer;
• Stress relief is performed by tempering in horizontal gas furnaces;
• Hardening of the roll barrel is performed by high-speed heating of the barrel in gas furnace and further high-speed cooling in water-air sprayer;
• Final stress relief and adjustment of the hardness is performed by high-temperature tempering in horizontal gas furnaces.

Work rolls for cold-rolling mills: 

• Isothermal annealing is performed in horizontal gas furnaces;
• Hardening of whole work roll body is performed by quenching in water-air sprayer;
• Stress relief is performed by tempering in horizontal gas furnaces;
• Hardening of the roll barrel is performed by induction hardening;
• Stress relief and adjustment of the final hardness is performed by low-temperature tempering in horizontal gas furnaces;
• Whenever it is required by drawing, specific surfaces of the roll can be hardened by nitriding, carburisation or chrome plating.

NKMZ backup rolls have an excellent combination of metallurgical and physical properties such as a compact porosity-free microstructure; good ductility and toughness values; high resistance to fatigue, wear and thermal cracking; uniform wear of roll barrel during operation. High physical and metallurgical properties are to be achieved throughout the optimal combination of pure steel, forging ratio and heat treatment processing.

Backup roll accessories: 

We assemble our Backup Rolls with labyrinth rings, keys, pins, bolts, covers, Inner Bearing Rings SKF made as per drawing requirements.

Mechanical properties of the barrel: 

• Hardness: 60-70 HS (depends on requirements);
• Maximum drop of hardness on depth of 75 mm: 5HS;
• Hardness variation of the roll barrel: 3 HS;
• Hardened layer depth: minimum 75-100 mm;
• Ultimate bending strength: 2500-2800 MPa;
• Tensile strength: 1400-1500 MPa;
• Modulus of elasticity: 210.000 MPa;

Mechanical properties of the necks: 

• Hardness: 35-50 HS (depends on requirements);
• Tensile strength: 1100-1300 MPa;
• Yield strength: 800-1000 MPa;
• Elongation: 7-12%;
• Impact strength: 20-30 J/cm2;
• Modulus of elasticity: 210.000 MPa;

NKMZ work rolls have an excellent combination of metallurgical and physical properties such as:

• Compact porosity-free microstructure; 
• Good ductility and toughness values; 
• High resistance to fatigue, wear and thermal cracking;
• Uniform wear of roll barrel during operation;
• Deep hardness penetration;
• High roll surface quality

Mechanical properties of the barrel: 

• Hardness: 85-100 HS (depending on requirements);
• Maximum drop of hardness on depth of 20 mm: 3HS;
• Hardness variation of the roll barrel: 2 HS;
• Hardened layer depth: minimum 20-25 mm (depends on requirements);
• Ultimate bending strength: 3500-4500 MPa;
• Bending deflection: 4-6 mm.

Mechanical properties of the necks: 

• Hardness: 35-60 HS (depending on requirements);
• Tensile strength: 850-1050 MPa;
• Yield strength: 650-980 MPa;
• Elongation: 18-25%;
• Impact strength: 25-40 J/cm2.

We focus on advanced technologies and highly-protective materials when it comes to packing our rolls. The package we utilise guarantees safe transportation of the cargo by road, railway and by sea, as well as safe multiple transshipments, and is suitable for transportation in all climate zones even in adverse weather conditions.

We provide anti-corrosion coating with a high level of moisture-resistant properties in full conformity with accepted standards, which ensures goods safety throughout one year of indoor storage.

Wooden materials used for packaging are fumigated and fully comply with the terms of the International Standard ISPM 15, which is evidenced by special marking signs.

• Online express analysis of chemical composition of steel in ladle;
• Online express analysis of gases content in steel in ladle;
• Hardness measurement after all heat treatments and during final acceptance by EQUOTIP devices; 
• Ultrasonic control is made in 2 stages: 1st stage before hardening, and 2nd stage during final acceptance;
• During final machining work rolls and intermediary rolls barrel surface and sub-surface can be tested by online Eddy-current Tester with submission of the relevant report; 
• Whenever it is required, roll surfaces can be checked by magnetic particle or dye-penetrant test; 
• High-precision tests to ensure right shape, dimensions and surface conditions.